Body Fat Calculator

Estimated body fat % from tape measurements.

Estimate body fat percentage using the US Navy circumference method (neck, waist, and hip for women).

How it works

The US Navy method estimates body fat percentage from height and circumference measurements: neck and waist for men, plus hips for women, using logarithmic formulas developed by the US Navy.

When it helps

It needs only a tape measure, which makes it a convenient alternative to scales and scans.

Worked example

A man who is 178 cm tall, with a 38 cm neck and an 86 cm waist, gets an estimate of about 17% body fat from the US Navy formula. For women the formula also uses the hip measurement, because women naturally carry more fat around the hips.

Measure on bare skin, keep the tape level and snug without pressing into the skin, and take each measurement two or three times. A 1 cm error at the waist can move the result by about one percentage point.

Putting the number in context

Healthy ranges differ by sex and age. As a rough guide, many fitness organizations consider about 10–20% typical for adult men and about 20–30% for adult women, with athletes often lower.

The method is best for tracking change over time: measure under the same conditions every few weeks — for example in the morning before eating — and watch the trend rather than any single reading. This is an estimate, not a medical assessment.

Frequently asked questions

How do I measure correctly?

Measure the neck just below the larynx, the waist at the navel (men) or narrowest point (women), and the hips at the widest point.

How accurate is it?

Typically within a few percentage points of lab methods, but measurement errors affect it.

Why is my result different from my smart scale?

Smart scales use electrical impedance, which is affected by hydration. Different methods often disagree by several percentage points.

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